Multi-stage absorption refrigeration system

ABSTRACT

There is provided an improved multi-stage absorption refrigeration system employing a highly concentrated solution of refrigerant to obtain an increased refrigeration effect relative to the quantity of input heat to the system as compared with a conventional system, comprising a multi-stage regeneratorcondenser system and at least a one-stage evaporator-absorber system provided with a pressure elevating device therebetween. In this evaporator-absorber system, the refrigerant from said regenerator-condenser system is vaporized in the evaporator, subsequently increased in pressure through the pressure elevating device and then absorbed at the increased pressure in the absorber.

United States-Patent n 1 Mamiya [451 Julyv3, 19 3 MULTI-STAGE ABSORPTIONREFRIGERATION SYSTEM [76] Inventor: Gohee Mnmiya, I I-6, MitsuzawaKamicho, Kanag'awa-ku,

Yokohama-shi, Kanagawa-ken,

, Japan [22] Filed: Sept. 15, 1971 [2]] Appl. No.: 180,640

[30] Foreign Application Priority Data Sept. 25, 1970 Japan ..45/8347852] U.S.Cl. 62/476, 62/483 51 Int. Cl. ..F25b 15/02 [58] FieldofSearch62/111,476, 483,

[56] References Cited v UNITED STATES PATENTS 1,265,037. .5/1918'.Bertsch 62/483 x 2,446,988 8/1948 F1oresetal...;..'. 62/483 6/I964Kaufman 62/476X 4/1951 Bernatetal. 62/483 Primary Examiner-William F.O'Dea AssistamEXaminer-Peter D. Ferguson Attorney'-Milton J. Wayne etal.

[57] ABSTRACT There is provided an improved multi-stage absorptionrefrigeration-system employing a highly concentrated solution ofrefrigerant to obtain an increased refrigeration effect relative to thequantity of input heat to the system as compared with a conventionalsystem, comprising a multi-stage regenerator-condenser system and atleast a one-stage evaporator-absorber system provided with a pressureelevating device therebetween,

In this evaporator-absorber system, the refrigerant from'saidregenerator-condenser system is vaporized in the evaporator,subsequently increased 'in pressure through the pressure elevatingdevice and then absorbed at' the increased pressure in the absorber.

4 Claims, 4 Drawing Figures,

PATENTEUJULs 1913 sum 1 or 4 MULTI-STAGE ABSORPTION REFRIGERATION SYSTEMthe refrigerant regenerated from the concentrated re-,

frigerant solution in the regenerator-condenser system is vaporizedunder low temperature and pressure conditions in the evaporator .tocreate a refrigeration effect. The refrigerant is subsequently increasedin pressure through the pressure elevating device and then absorbed atthe increased pressure in the absorber by the refrigerant introducedthereinto from said regeneratorcondenser system directly or through theleading evaporator-absorber system. The concentrated refrigerantsolution is thus produced and returned to said regenerator-condensersystem from the final absorber.

The invention will be described in detail with reference to theaccompanying drawings, wherein;

FIG. 1 is a schematically illustrated flow diagram for a multi-stageabsorption refrigerator according to the invention, I FIG. 2 is adiagram. showing the cycle of refrigerant vapor and solution in theapparatus of FIG. 1 with reference to pressure, temperature andconcentration,

FIG. 3 is a schematically illustrated flow diagram for anothermulti-stage absorption refrigerator according to the invention, and

FIG. 4 is a diagram showing the cycle of refrigerant vapor and solutionin the apparatus of FIG. 3 with reference to pressure, temperature andconcentration.

FIG. 1 shows one of the embodiments of the multistage absorptionrefrigerator according to the invention, which has six stages ofregenerators and condensers. The apparatus comprises regenerators l to6, condensers 7 to 12, an evaporator 13, a pressure elevating device 14and an absorber 15. Part of a concentrated refrigerant solution isdelivered through line 16 to the first regenerator l, where it is heatedby a vaporous external heat source which is supplied to heater l8disposed in the regenerator 1 through line 17, thereby regenerating arefrigerant solution. The diluted residue in the first regenerator Ithen passes through outlet 19 to heat exchanger 20, while therefrigerant vapor regenerated in the first generator 1 passes throughoutlet 21 to the condenser 7 disposed in the second regenerator 2 andheats thereby another part of the concentrated refrigerant solutiondelivered to the second regenerator 2 through line 22 to regenerate arefrigerant vapor from the heated solution, whereby it is condensed to aliquid which subsequently passes to the heat exchanger throughoutlet'23. The diluted residue of the refrigerant solution from whichthe refrigerant vapor has been regenerated in the second regenerator 2passes to heat exchanger 25 through outlet 24.-The refrigerant vapor inthe second regenerator 2 passes through outlet 26 to the condenser 8disposed in the third regenerator 3 and heats thereby a further part ofthe concentrated refrigerant solution which has been flashed into thethird regenerator through line 27 to regenerate a refrigerant vapor fromthe solution, whereby it is condensed into a liquid which subsequentlypasses to the heat exchanger 25 through outlet 28. A diluted residue ofthe refrigerant solution from which the refrigerant vapor has beenregenerated in the third regenerator 3 passes through outlet 29 to heatexchanger 30. The refrigerant vapor in the third regenerator 3 passesthrough outlet 31 to the condenser 9'disposed in the fourth regenerator4 and heats thereby another part of the concentrated refrigerantsolution which has been delivered to the fourth regenerator 4 throughline 32 to regenerate a refrigerant vapor from the solution, whereby itis condensed into a liquid which subsequently passes to the heatexchanger 30 through outlet 34.

In each following regenerator 4, 5, 6 such processes as described aboveare also carried out. However, the refrigerant vapor produced in thefinal regenerator 6 is introduced through outlet 46 to a condenser 12 inan evaporative condenser 47 or a condenser of a cooling water type tocondense it into a liquid which subsequently passes through line 48 toflow into the combined line 69. On the other hand, the remainingrefrigerant at high temperature produced in the regenerators excludingthe sixth regenerator 6 is cooled in the heat exchangers 20, 25, 30, 35and 40 by the parts of the concentrated refrigerant solution which aredistributed from the absorber 15 to the regenerators through outlet 49,pump 50, line 51 and distributing lines 52 to 57, the heat exchangersand then lines 16, 22, 27, 32, 37 and 42 respectively.

Each cooled refrigerant flows through each reducing valve 64, 65, 66, 67or 68 into the combined line 69 together with the refrigerant from thecondenser 12. The confluent flow of the refrigerant through line 69is-introduced at a reduced pressure through reducing valve 70 to theevaporator 13, so that it is vaporized at a low temperaturecorresponding to its reduced pressure maintained'in evaporator 13,thereby creating the target refrigeration effect for cooling a fluidpassing through a heat exchanger 71 disposed in the evaporator 13. Onthe other hand, the dilute refrigerant solutions which have been cooledthrough the respective heat exchangers 20, 25, 30, 35, 40 and 45 arereduced in pressure through the respective reducing valves 72 to 77 andflow into the combined line 78. The combined solution is reduced inpressure through reducing valve 79 and then is flashed into the absorberl5.

The refrigerant vapor produced by the refrigeration effect in theevaporator 13 is transferred through the pressure elevating device 14 tothe absorber 15 in which it is absorbed by the dilute refrigerantsolution flashed into the absorber. The heat generated by the absorptionat this time is absorbed by cooling water which passes through cooler 80disposed in the absorber l5.

In conventional apparatus, evaporators such as evaporator 13 andabsorbers such as absorber l5 maintain the refrigerant vapor at constantpressure. Theapparatus according to this invention employs a more highlyconcentrated refrigerant solution for obtaining a greater refrigerationeffect than conventional apparatus. Therefore, in a case where the vaporis passed to the absorber 15 without a pressure increase from thepressure elevating device 14 the temperature of the dilute refrigerantsolution in the absorber must be lowered to effect the same degree ofabsorption. However, it is difficult to obtain such lower temperature byapplying cooling water such as well water or water supplied from acooling tower.

In view of this fact, a pressure elevating device 14 such as an electricfan connecting the evaporator 13 and the absorber therewith is providedin this invention. In the arrangement, the refrigerant vapor produced asa result of the evaporation for creating the refrigeration effect in theevaporator 13 is fed through passage 81 to the pressure elevating device14, where it is increased in pressure and then at the higher pressure isintroduced through passage 82 to the absorber 15 which is maintained atthe same high pressure. In other words, pressure elevating device 14 isprovided for introducing the refrigerant vapor at a higher pressurecorresponding to the temperature of the solution in the absorber whichtemperature may be attained easily by applying cooling water such aspreviously described. I e

The refrigerant vapor thus introduced into the absorber 15 is absorbedeffectively by the dilute refrigerant solution which has been fed to theabsorber 15 through the reducing valve 79, whereby the diluterefrigerant solution is converted into a concentrated refrigerantsolution. The concentrated refrigerant solution is discharged fromoutlet 49 of the absorber through line 51 to pump 50'disposed therein,by which it is pressurized. The pressurized solution is distributed tothe regenerators l to 6 through distributing lines 52 to 57, the firstheat exchangers 20, 25, 30, 35, 40 and 45, regulating values 58 to 63and second heat exchangers 83 to 88, respectively. On the way to theregenerators the respective solutions are heated by the first heatexchangers and then supplementally heated by the second heat exchangersup to the necessary temperature for effecting their subsequentvaporization in the regenerators as previously described.

The refrigeration effect thus is obtained by repeating the cycleoperation set forth above in the refrigerator.

FIG. 2 illustrates a cycle of a refrigerant solution with reference topressure, temperature and concentration in the case where water is usedas a refrigerant material and a water-lithium bromide solution is usedas the refrigerant solution in the apparatus shownin FIG. 1.

Concentrations referred to hereinafter and in the drawings are those forlithium bromide in weight by percent in the refrigerant solution.

In this example, a 45% solution of lithium bromide is distributed from'the absorber to the respective regenerators wherein the distributedsolution is vaporized up to a 50% solution, and the resultant solutionsare subsequently returned to the absorber 15 after they are cooled bythe heat exchangers 20, 25, 30, 3,5, 40 and 45.

Referring to FIG. 2, the first 45% solution at a pressure of 30.1588 mm,at a temperature of 258 C corresponding to point A, is introduced intothe first regenerator 1, where it is heated to 267 C at point 8,, andthus a refrigerant vapor at 233 C at point C, is generated from it,whereby it is concentrated to a 50% solu tion, which is a diluterefrigerant solution. The second 45% solution at a pressure of a 12.5302atm. and at a temperature of 214 C corresponding to point A; isintroduced into the second regenerator 2, where it is heated to atemperature 223 C at point B, by the latent heat of condensation of theregenerated vapor introduced from the first regenerator at a temperature233 C at the point C, and thus a refrigerant vapor is regenerated fromit at a temperature of 189 C at point C whereby it is concentrated to a50% solution as a dilute refrigerant solution.

In such processes as described above, the third, fourth, fifth and sixth45% solutions corresponding to points A A A and A, are introduced intothe respective regenerators, where they are heated to the temperaturesshown at points B ,'B,, B and B, by the latent heat of condensation ofthe regenerated vapors introduced from the leading regeneratorscorresponding to points C C C and C, respectively and thus refrigerantvapors corresponding to C C C and C are respectively regenerated fromthem, whereby they are concentrated to 50% solutions as diluterefrigerant solutions. Subsequently, the regenerated vapors excluding Care condensed to liquids and then cooled to a temperature of 40 C by theheat exchangers 20, 25, 30, 35 and 40 respectively, while the remainingvapor C is condensed at a temperature of 35 C to a liquid at the sametemperature by the evaporative condenser 47.

All the condensed refrigerants flow into the evaporator through line 69and then the combined liquid refrigerant is vaporized under theconditions corresponding to point D to create the refrigeration effect.

For effecting the absorption of the resultant vapor by the 50% solutionin the absorber under the same pressure as the evaporator, it would benecessary for the solution in the absorber to be cooled to a temperaturebelow 20 C. However, according to the invention, the pressure of therefrigerant vapor corresponding to the point D is raised to the pressureco'rresponding to point E by the pressure elevating device 14 andintroduced into the absorber 15 which is maintained at the same elevatedpressure, while the 50% solution is introduced from the respectiveregenerators to the absorber in a combined flow through the line 78after being cooled by the respective heat exchangers. In thisconnection, the refrigerant vapor is absorbed by the dilute refrigerantsolution of 50% lithium bromide under the conditions corresponding topoint F so as to change it to a concentrated refrigerant solution of 45%lithium bromide. Therefore, the above absorption process may be carriedout effectively if the solution in the absorber is cooled to atemperature of 35 C or lower.

Alternatively, when the refrigerant vapor is pressurized to a pressureat the point B, the refrigerant vapor may be absorbed by the 50%solution in the absorber at the same pressure. In this case, aneffective absorption would be carried out by cooling the solution in theabsorber to a temperature of 45 C or lower which may be attained moreeasily than in the former case.

In this example, if the 45% solutions introduced into the regenerators lto 6 are 10,000 kg/h, 7,437 kg/h, 5,336 kg/h, 4,703 kglh, 3,854 kg/h and3,250 kg/h respectively, the regenerated refrigerants in theregenerators amount to 1,000 kg/h 743.7 kg/h, 583.6 kg/h, 470.3 kg/h,385.4 kg/h and 325 kg/h, respectively. The total amount of theregenerated rerfrigerant is 3,508 kg/h, so that the corresponding totalrefrigeration capacity is equivalent to 1,963,647 Kcal/h. Thesubstantial refrigeration capacity becomes 1,767,282 Kcal/h (196,364 X0.9), assuming that the heat exchanging efficiency in the heat exchanger71 is 0.9.

The total quantity of heat externally supplied to the heaters 18 and 83to 88 is 836,354 Kcal/h, assuming that the heat exchanging efficiency ofeach heater is 0.9. Of the total quantity of the input heat, the heater18 disposed in the first regenerator 1 requires a quantity equivalent to539,855 Kcal/h and the respective heaters 83 to 88 for heatingsupplementally the dilute refrigerant solutions require quantitiesequivalent to 120,528.13 Kcallh, 75,521 Kcal/h, 49,469.8 KcaI/h, 29,4102Kcal/h, 14,736.6'Kca1/h and 6,832.2 Kcal/h, which amount to 296,499Kcal/h. Accordingly, the ratio of the refrigeration capacity to thetotal quantity of the input heat is as follows.

1,767,282 Kcal/h 836,354 Kcal/h 211.3 100 The conventional absorptionrefrigerator provides a rerigeration capacity of 70 Kcal/h relative toan input heat of 100 Kcal/h. Comparing the refrigerator according to thepresent invention with the conventional refrigerator the former has arefrigeration capacity approximately three times greater (21 1.3/703.01).

FIG. 3 shows a diagram of another embodiment of the refrigeratoraccording to the present invention wherein the refrigerant solution iscirculated successively through all the refrigerators in series.

In the refrigerator shown in FIG. 3, a concentrated refrigerant solutionis introduced through line 113 and valve 109 from a central heatexchanger 125 to a first regenerator 101, where it is heated by anexternal heat source supplied to heat exchanger 126 disposed in thefirst regenerator, thereby regenerating a refrigerant vapor and thusproducing a dilute residue. The resultant solution with the lowerconcentration of the refrigerant is fed to a second regenerator 102through line 117 passing through the heat exchanger 125 and throughvalve 110, while the resultant vapor is fed to condenser 105 disposed inthe second regenerator 102 through line 121.

On the way to the second regenerator 102, the dilute refrigerantsolution is cooled to the necessary temperature by the heat exchanger125.,The refrigerant vapor passing through the condenser 105 heats thedilute solution flashed into the second regenerator 102 from. the firstregenerator 101 by its heat of condensation to regenerate a refrigerantvapor from the solution and produce a diluted residue thereof, wherebyit is condensed to a refrigerant liquid. The diluted residue of thesolution in the second regenerator 102 with lower concentration of therefrigerant than in the first regenerator 101 is introduced to a thirdregenerator 103 through line 118 passing through the heat exchanger 125and through valve 111, while the regenerated vapor is fed to a condenser106 disposed in the third regenerator 103 through line 122.

On the way to the third regenerator, the lower concentrated solution iscooled to the necessary temperature by the heat exchanger 125. Therefrigerant vapor in the condenser 106 heats the lower concentratedsolution flashed into the third regenerator 103 to regenerate arefrigerant vapor from the solution and produce a diluted residuethereof, whereby it is condensed to a refrigerant liquid. The dilutedresidue of the solution with lower concentration of the refrigerant thanin the second regenerator is introduced to a fourth regenerator 104through line 119 passing through the heat exchanger 125 and throughvalve 112, while the refrigerant vapor is fed to condenser 107 disposedin the fourth regenerator 104 through line 123. On-the way to the fourthregenerator, the lower concentrated solution is cooled to the necessarytemperature by the heat exchanger 125.-

The refrigerant vapor in the condenser 107 heats the lower concentratedsolution flashed into the fourth regenerator to regenerate a refrigerantvapor from the solution and to produce diluted residue thereof, wherebyit is condensed to a refrigerant liquid. The diluted residue of thesolution with lower concentration of the refrigerant than in the thirdregenerator is passed to the heat exchanger 125 through line to becooled to the necessary temperature, while the refrigerant vapor ispassed through line 124 to heat exchanger 108, where the vapor iscondensed to a refrigerant liquid.

The refrigerant condensed in the condenser 108 and the other refrigerantcooled in the heat exchanger 125 may be combined as a fluid to besubsequently vaporized for creating a refrigeration effect and thenabsorbed at an increased pressure of the resultant vapor in a singlestage of the evaporator and the absorber which are connected to thepressure elevating device as shown in FIG. 1. However, in the embodimentshown in FIG. 3, the respective refrigerants are to be processed foreffecting evaporation, pressurization and then absorption in therespective stages of the units, each of which comprises an evaporator, apressure elevating device and an absorber. In this embodiment, a morecomplicated system is required, while the necessary energy for drivingthe pressure elevating device is lower in comparison with the embodimentof FIG. 1.

The evaporation and absorption processes in FIG. 3 are now explained indetail as follows.

The respective refrigerants regenerated in the regenerators and thencondensed in the condensers are fed through reducing valves 131 to 134to evaporators 127 to 130, where they are vaporized to create therefrigeration effect for cooling fluids passing through respective heatexchangers 147 to 150 disposed in the evaporators'. The resultant vaporsthen pass through pressure elevating devices 135 to 138 and areintroduced at the increased pressure to absorbers 139 to 142,respectively.

The dilute refrigerant solution from the final regenerator 104 isflashed into the first absorber 139 through reducing .valve 155 and thenabsorbs the pressurized vapor which has been introduced from the firstevaporator 127 to the absorber at the same pressure through the pressureelevating device 135.

The resultant solution in the first absorber 139 is then introducedthrough pump 143 and reducing valve 156 to the second absorber 140,where it absorbs the vapor which has been produced in the secondevaporator 128 and then increased in pressure by the pressure elevatingdevice 136. The resultant solution in the second absorber is thenintroduced via pump 144 and reducing valve 157 to the third absorber141, where it absorbs the vapor which has been produced in the thirdevaporator 129 and then pressurized by the pressure elevating device137. The resultant solution in the third absorber 141 is then introducedthrough pump and reducing valve 158 to the fourth absorber 142, where itabsorbs the vapor which has been produced in the fourthevaporator 130and then elevated in pressure by the pressure elevating device 138. Theresultant concentrated solution of the refrigerant in the final absorber142 is fed to the central heat exchanger 125 through pump 146 and line159.

In the heat exchanger-125, the concentrated solution is heated andpassed to the first regenerator 101 through line 113 and thus theprocess of the refrigerant solution from the first regenerator 101 tothe fourth regenerator 104 is repeated as previously set forth forcreating the refrigeration effects in the respective evaporators.

The refrigerant solutions in the respective absorbers 139 to 142 arecooled by cooling water passing through coolers 151 to 154 disposedtherein.

FIG. 4 shows an example of the cycle of the refrigerant solution withreference to pressure, temperature and concentration, when water is usedas a refrigerant material and a water-lithium bromide solution is usedas the refrigerant solution in the apparatus shown in FIG. 3.

The concentrations shown in FIG. 4 indicate those of lithium bromide inweight by percent in the solution.

Referring to FIG. 4, when the aqueous solution of lithium bromidecorresponding to point A is introduced to the first regenerator 101 andheated therein, a refrigerant vapor of water corresponding to point C isregenerated from the solution. The diluted residue of the solution at B,is cooled by the heat exchanger 125, reduced in pressure by the reducingvalve 110 and fed to the second regenerator 102 under the conditioncorresponding to point A When the solution at A is heated by therefrigerant vapor at C to be given a latent heat of condensationthereby, it regenerates a refrigerant vapor corresponding to point Cwhereby it is changed to'a solution corresponding to point B Bysuccessively carrying out such processes as the above in order to changethe state of the refrigerant solution from that at point B, to the stateat points A B A and finally B refrigerant vapors corresponding to pointsC and C are obtained.

The rerigerant at the point C is condensed into a liquid which issubsequently vaporized in the first evaporator 127 under the conditioncorresponding to point G, thereby creating a refrigeration effect. Theresultant vapor is increased in pressure at point E through the pressureelevating device 135 and thus introduced to the first absorber 139,where it is absorbed by the refrigerant solution introduced through avalve 155 at point D, whereby a concentrated solution at point F isproduced.

The refrigerant at the point C, is condensed into a liquid which issubsequently vaporized in the second evaporator 128 under the conditioncorresponding at the point G, thereby creating a refrigeration effect.The resultant vapor is increased in pressure at point E through thepressure elevating device 136 and thus in- I troduced to the secondabsorber 140, wherein it is absorbed by the refrigerant solutionintroduced from the first absorber 139, whereby a more concentratedsolution at point F is produced. By successively carrying out suchprocesses as described above, the refrigerants at the points C and C arealso vaporized in the third and the fourth evaporators 129 and 130 underthe condition at the point G, and more concentrated solutions at pointsF and F are produced in the third and the fourth absorbers 141 and 142,respectively.

The final concentrated solution at the point F in the final absorber 142is then passed to the heat exchanger via the pump 146 and the line 159.

When a 43.9% aqueous solution of lithium bromide at a pressure 13.97atm. and at a temperature of 217 C corresponding to the point A isintroduced into the first regenerator 101 from the heat exchanger 125 ata flow rate of 10,000 kg/h and the cycle operation as shown in FIG. 4 iscarried out, quantities of heat of 565,181.8 Kcal/h and 35,4673 Kcal/h(i.e., total amount of 600,649.] Kcal/h) are required to be supplied tothe heat exchanger 126 and respectively, whereby a refrigeration effectequivalent to l,340,684.3 Kcal/h is obtained over all. The refrigerationcapacity obtained is thus 223.2 Kcal/h relative to an input heat to thesystem of 100 Kcal/h (l,340,684.3 600,649.l X 100 223.2).

The conventional absorption refrigerator provides a refrigeration effectof 70 Kcal/h relative to a supplied quantity of heat of 100 Kcal/h.Comparing the illustrated apparatus of the present invention with aconventional refrigerator, it has a refrigeration capacity approximately3.19 times that of the conventional refrigerator (223.2 70 3.19). I

According to the invention, since a more highly concentrated solution ofrefrigerant is employed than in the conventional refrigerator, a vaporis generated with a considerably higher temperature than in theconventional refrigerator for the same temperatures of the refrigerantsolutions. For example, in the embodiment shown in FIG. 2, vapor at atemperature of 233 C is regenerated from a 50% solution of lithiumbromide at a temperature of 267 C, while vapor at a temperature of C (atpoint C-,) is regenerated from a 65 %'solution at a temperature of 267C.

In view of this fact, a system of the multi-stage type according to theinvention is distinguishably suitable for employing a more concentratedrefrigerant solution, thereby obtaining a greater refrigeration effectthan heretofore known.

Further, according to the present invention, even if an aqueous solutionof lithium bromide is employed as a refrigerant solution,crystallization of lithium bromide will not occur under the lowertemperature employed in the present system, because the concentration oflithium bromide employed is lower than in the conventional system.

What I claim:

1. An absorption refrigeration system comprising a plurality ofsuccessive regenerator-condenser vessels each having a heat exchangertherein, an evaporator, an absorber, and a concentrated refrigerantsolution in said system, said system further comprising means forapplying external heat to the heat exchanger of a first one of saidvessels, means for passing concentrated refrigerant solution from saidabsorber to each of said vessels for absorbing heat from the respectiveheat exchanger to regenerate a refrigerant vapor and a dilute residue ofsolution therein, means returning said diluted residue from said vesselsin common to said absorber, means for passing said regenerated vaporfrom all but a second one of said vessels to the heat exchanger of asuccessive vessel for condensation therein to a liquid, means forcondensing said vapor from said second vessel to a liquid, means forpassing the liquid from said means for condensing and from the heatexchanger of all but said first of said vessels to said evapo- 3. Therefrigeration system of claim 1 wherein said means for passingconcentrated refrigerant solution includes separate regulating valvemeans for each said vessel.

4. The refrigeration system of claim 1 wherein said means forcondensingsaid vapor from said second vessel to a liquid comprises anevaporative condenser.

1. An absorption refrigeration system comprising a plurality ofsuccessive regenerator-condenser vessels each having a heat exchangertherein, an evaporator, an absorber, and a concentrated refrigerantsolution in said system, said system further comprising means forapplying external heat to the heat exchanger of a first one of saidvessels, means for passing concentrated refrigerant solution from saidabsorber to each of said vessels for absorbing heat from the respectiveheat exchanger to regenerate a refrigerant vapor and a dilute residue ofsolution therein, means returning said diluted residue from said vesselsin common to said absorber, means for passing said regenerated vaporfrom all but a second one of said vessels to the heat exchanger of asuccessive vessel for condensation therein to a liquid, means forcondensing said vapor from said second vessel to a liquid, means forpassing the liquid from said means for condensing and from the heatexchanger of all but said first of said vessels to said evaporator forvaporization therein to produce a refrigeration effect, and means forincreasing the pressure of the vapors in said evaporator and applyingthem to said absorber for absorption by the diluted residue therein. 2.The refrigerator system of claim 1 further comprising heat transfermeans coupled between said means returning said diluted residue and saidmeans for passing said concentrated refrigerant solution of eachrespective vessel.
 3. The refrigeration system of claim 1 wherein saidmeans for passing concentrated refrigerant solution includes separateregulating valve means for each said vessel.
 4. The refrigeration systemof claim 1 wherein said means for condensing said vapor from said secondvessel to a liquid comprises an evaporative condenser.